This work will investigate the potential of a nanoporous silicon membrane (pnc-Si) to provide revolutionary performance in protein filtration. Because the novel membrane material is molecularly thin (15 nm), it is predicted to improve the efficiency of both dialysis and convective flow filtration. Because the material is made from silicon, manufacturing is scalable and readily integrated into microfluidic devices. Thus the material may enable a host of small scale analytical, preparative, and therapeutic devices. Despite being molecularly thin, the porous membranes are strong enough to be used in pressurized devices. Aim 1: Quantitatively characterize the performance of pnc-Si membranes for diffusion- based separations We will quantify the function of pnc-Si membranes in diffusion-based separations. Using a membrane library with a range of porosities and pore sizes, we will determine: 1) rejection sizes of model species and protein mixtures; and 2) the mobility of small solutes, model particles, and proteins through pnc-Si membranes. Work will directly address the potential deleterious effects of protein adsorption by measuring small solute transport in the presence and absence of high protein concentrations. Membranes will be directly inspected for evidence of biofouling by transmission electron microscopy. If protein adsorption slows transport, membranes will be modified by grafting with short PEG molecules, and the modified membranes re-characterized. Aim 2: Quantitatively characterize pnc-Si membranes for pressurized flow applications Here we will examine the ability of pnc-Si membranes to filter protein rich solutions in pressurized minichannels and centrifuge tubes. In these systems we will characterize the ability of pnc-Si membranes to separate small solutes from proteins, concentrate large species, and fractionate complex mixtures by size. We will measure volume flow rates and quantify any reduction of flow rate when protein is concentrated in the sample. We will minimize biofouling by direct inspection and surface modification as in Aim 1. Because the mechanical properties of pnc-Si membranes are vital to applications in pressurized systems, we will quantitatively determine the likelihood of membrane bursting under different pressures. This project will characterize the ability of a new silicon-based, nanoporous membrane to filter biological fluids. The molecularly thin nanomembranes have the potential to revolutionize filtration rates and are the first filter material that can be integrated into microfluid systems as modules. These abilities are expected to enable a host of new small scale clinical and diagnostic devices. [unreadable] [unreadable] [unreadable]